Spinach Mushroom Gratin is a lovely side dish that’s filled with iron-rich dark green spinach, mushrooms, creamy ricotta, cheeses, and all topped off with a crunchy bread crumb topping. This casserole dish is so good!
This was so good that even my husband, who doesn’t like cooked spinach at all loved it, and I caught him sneaking bites of it!
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It’s the perfect side dish for any family gathering, especially a nice holiday meal.
This side dish can be made ahead, making it perfect to take to a family holiday celebration, or to a friend who may need food, like a new mom or a sick friend.
Make it easy on you
When I take a dish to someone’s house I always make it in a disposable aluminum pan, or in a dish from the dollar store. Then no one has to return your pan to you!
If making this Spinach Mushroom Gratin in advance, prepare it through step 8 (where you drizzle the butter over the top). Allow it to cool, cover it tightly with foil or a lid, and refrigerate it or freeze it.
When you’re ready to bake it, simply thaw it in the fridge overnight if it was frozen, and continue with the baking instructions on the recipe card. (Bake at 350º F for 30 minutes or until the casserole is browned, puffed, and bubbling.)
How to thaw the frozen spinach
I bought two boxes of frozen spinach, which made it nice and easy to get 20 ounces. Frozen spinach also comes in bags, but I’ve never seen a 20 ounce bag of it, so I recommend going with two boxes, just for size reasons.
That being said, of course you can use the bagged frozen spinach and guesstimate 20 ounces. The process of thawing and draining will be the same.
Remove the frozen block of spinach from the paper box and place it on a microwave safe plate.
Microwave the spinach on high power for 3-7 minutes (microwave times will vary based on different power levels). Stir after every couple of minutes to try to break up any icy chunks. The spinach is done when there are no more icy spots.
Alternatively to microwaving it, you can thaw it under warm running tap water. Remove the frozen block of spinach from the paper box, and place the block in a mesh strainer and run it under very warm water. Feel around for icy chucks, and break them apart with your fingers.
How to drain the liquid off the spinach
For this dish you want the spinach to be pretty dry, so in order to get that, you’ll need to squeeze as much liquid out of thawed spinach as possible. There are a couple of ways the liquid can be drained off.
1. Place the thawed spinach in a fine mesh sieve, and allow the liquid to drain. Then take a wooden spoon and press down on the spinach to press all the liquid out.
2. You can also grab a handful of spinach and squeeze the water out of the spinach. Your hands will get a little messy, but that’s fine.
3. Place the thawed spinach in a clean dry cotton cloth towel. Wrap the towel around the spinach and squeeze the water out of the spinach.
Want to make this a little lighter in calories?
Use light cream cheese instead of regular cream cheese. It won’t be quite as creamy and rich in flavor, but it will still work in the dish.
Also, you can use reduced fat Monterey Jack cheese instead of regular.
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Spinach Mushroom Gratin Recipe
Spinach Mushroom Gratin
- 2 bunches green onions chopped
- 2 tablespoons olive oil
- 8 ounces mushrooms sliced
- 20 ounces chopped frozen spinach thawed
- ½ teaspoon garlic powder
- 1 teaspoon salt
- pinch of cayenne pepper
- ½ teaspoon dried oregano
- 8 ounces ricotta cheese divided use
- 3 eggs divided use
- 4 ounces cream cheese softened
- 6 ounces Monterey Jack cheese grated, divided use
- 1 cup Panko
- ¼ cup unsalted butter melted (½ stick)
- Heat the oil in a medium saucepot. Once the oil is hot, sauté the chopped green onions in the oil, until the onions are soft and starting to brown, about 5-7 minutes.
- Add the sliced mushrooms, and cook until the mushrooms have released their liquid and the liquid has cooked off, about 7-10 minutes.
- Stir in the spinach, and cook 3 minutes, stirring constantly.
- Season the mixture with the garlic powder, salt, cayenne pepper, and oregano. Remove from heat.
- Stir in 4 ounces of ricotta, 2 eggs, cream cheese, and 1/3 of the grated Monterey Jack cheese.
- Grease a 9×9-inch casserole dish with butter or non-stick spray. Spoon the spinach mixture into the prepared casserole dish, and smooth out the top so it isn’t lumpy.
- In a separate medium bowl, combine remaining egg with remaining 4 ounces ricotta, and remaining grated Monterey Jack cheese. Spread the cheese mixture over the top of the spinach mixture.
- Sprinkle the Panko bread crumbs over the top of the cheese mixture, and drizzle with melted butter.
- Bake at 350º F for 30-40 minutes or until casserole is browned, puffed, and bubbling.